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dual parallel vs mono bridged fiasco

Discussion in 'Amps and Cabs [BG]' started by cactus pony, Sep 25, 2013.


  1. Hey all my 410XL currently stop working,

    Any insight would be great. My current set up is a Hartke LH1000 amp head powering a Hartke 4x10XL (400watts 8ohms) and a Fender Bassman 1x15 (250watts 8ohms). I have always used it in dual parallel mode (2 x 320 watts at 4ohms) and its been great, using the balance nob to give the 410 a bit more volume than the 115. We are doing some recording this weekend where I only need the 4x10 and the manual states if you are only using one cab (my one 4x10) you must use a speakon cable and switch the button to bridged mode.

    I went to Guitar Center and they sold me a LIVE WIRE ELITE SPEAKER cable after giving them all this info. I came home and switched the button to BRIDGED mode and connected my LH1000 to my 4x10 and had no sound until I turned the volume to 2 and had a loud pop and then no sound at all.

    After that I reconnected everything like i had it before in dual parallel mode and my 1x15 worked but my Hartke 4x10 made no noise at all. Did they sell me the wrong cable? How did my 4x10 cab stop working? Thanks for any help!
     
  2. Only thing I could imagine is the amp did not go into bridged mode properly and blew your cab out. I also don't know why they would tell you to go into bridged mode with a single cab when the channel A output should have done just fine for low power use?
     
  3. Hi.

    Had to even RTFM, because I didn't quite believe that's what they ment.
    They sure did.
    At least the way I read it.

    The only reason (IMO not a very good one with modern amps either) I can think of to do it is to avoid future imbalance problems in bridge mode if only one amplifier module has been in use.

    I've came across plenty of 20yr+ old PA amps that work well in single channel mode, but using the bridge mode (for the first time perhaps) has resulted very weird behaviour that can be traced to the dissimilarily behaving power amp sections.

    Another IMO peculiar "feature" of the amp in question is the suggestion to use a standard Speakon cable, not the usual bridge (+1/+2) cable, but I assume that it's because they decided that a phone jack is good enough for low power application and Speakon is only used for the bridged mode.

    Perhaps Larry could shed some light into this?

    Regards
    Sam
     
  4. What you said makes some sense and I was surprised that manual said to use bridged mode! Even more of a surprise when you follow the manual and your cab goes "POP".
    I don't see Larry's name on schematics, only Samson but maybe he can help with a word to the service manager.
     
  5. will33

    will33

    May 22, 2006
    austin,tx
    This is peculiar.....you shouldn't need a speakon cable because of the connector but because of the connections?

    Remember the older poweramps where in order to bridge them, you hooked up some jumpers or wired things together in such a way (externally) so as to put the positives together and hook them up to a common ground?
     
  6. Thank you all for your replies! I'll call Hartke's service line today and see what they have to say.
     
  7. In bridge ground is immaterial as it's not used. Channel One becomes the ":hot" and Channel Two becomes the "cold".

    OP do the battery test on your 4x10 and see if it is actually functioning.
     
  8. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    SEPA
    I can tell you that I have been using a LH1000 in bridged mono into a Hartke Vx-410 (400W, 8 ohm) and it has worked just fine. Since the Vx-410 has only 1/4" phone in, I bought a Speakon->Phone cable. No issues.

    I've since uprated the cab to a GK Neo 412 and it's Speakon->Speakon. Still in bridged mono. Still working fine.

    Does the 410 not work and the 115 always work no matter which side of the amp you plug it into?
    Be interesting to see what single-point failure there is in a cab that could result in total silence. Crossover, maybe?

    I'll have to go reread my manual again. I didn't get that bridged was required for a single cabinet - but since I planned to anyway I probably didn't read all the fine print...
     
  9. Thanks Paul, I will try battery test when I get home.
     
  10. From the manual: If you are using the LH1000 with a single cabinet of 4 ohms or 8 ohms, set the
    BRIDGE mode switch to BRIDGE and use a standard Speakon cable to connect
    your cabinet.

    It is totally silent on both sides of the amp...Everything with these cabs and amp have worked perfectly fine until I tried using bridge mode last night. My 410 only has 1/4inch in's so I bought a Speakon>1/4" cable. Only the cable package didn't say SPEAKON it said SPEAKER. Is that the same cable or is there a difference?
     
  11. Please do, it's the first place to start. Do the same test on your 15. to make sure of correct polarity.

    Using a 1/4" Phone cable in bridge is dangerous as the barrel of the connector is live with respect to ground. The tip is twice as live with respect to the barrel.

    As for your speakon cable, often when in bridge the wiring should be +1 >> +1 and -1 >> +2. The plusses at the amp end only, it won't work t'other way around. If the amp has a dedicated "Bridge" speakon the wiring is the normal +1 >> +1 and -1 >> -1.
     
  12. FunkHead

    FunkHead Supporting Member

    Mar 10, 2007
    Speakon is a different cable. It is also plugged into a different place on back of the head. My guess is that you fried something on one side of the LH1000. Based on your post that mysteriously disappeared where you asked if Speaker and Speakon were the same thing, You used the wrong cable. Also, If using more than one Cabinet, It's recommended to use the two separate 1/4" output Jacks and NOT Bridge mode. Bridge is for one 4 ohm Cabinet. There is also a fuse that may have blown in the fuse sled at the A/C Power input.
     
  13. In dual parallel I have been using two separate 1/4" speaker cables and plugged one into each side of the amp. The cable I bought yesterday has a Speakon type connector on one end, which I plugged into the connector on the back of the amp, and on the other end is a 1/4" which went into my 410. I just don't understand how I fried anything following the manual and using what I thought was the right cable.
     
  14. If you want to bridge retrofit NL4 speakon sockets into your cabinets. It's a simple job and worth every penny of the about $5 per socket. this avoids the pitfalls of bridge into Phone jacks.
     
  15. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    SEPA
    Per the manual, yes, I went and downloaded it again and yes, it does say that...

    There are a couple of other places on that page where emphasis is used: "MUST". So I'd interpret this paragraph more in terms of a suggestion or recommendation.

    It's a suggestion I took, tho, and did it exactly the way you have, with a Speakon->1/4" cable. Specifically, this one:
    http://www.musiciansfriend.com/accessories/live-wire-elite-12-gauge-speakon-1-4-speaker-cable (In Real Life, the 1/4" plug is MUCH more substantial than that picture...)

    So clearly, this _can_ work...

    Which points to either defective amp, since this is a connection you haven't tried before, or defective cable (somehow).

    The cable doesn't make power, so I'm confused as to how a wiring defect there could affect the cab, especially at low volume settings. A Speakon->1/4" cable _should_ have standard (+1 -> +1, -1 -> -1 ) connections, which is appropriate for the LH1000 since it has a dedicated Bridge output.

    (Per the safety warnings mentioned above, and good practice generally, always make these hookups with everything powered off...)

    Good luck with your conversations with Hartke - they have a reputation for good service.
     
  16. You did what you were supposed to do so this is not your fault. "Speakon" is used generously for naming a twist lock speaker connector, "Speakon" is actually a registered trademark for the connector developed by Neutrik. Since your amp has a separate dedicated connector for bridged mode a speaker cable with the standard wiring applies, you do not need a "bridged mode" cable.
    Speaker cabs are strictly passive, if it worked fine with the 1/4" to 1/4" before then nothing bad SHOULD have happened with a "speakon" to 1/4" speaker cable. This must be an amp fault.
     
  17. Thank you all for your help! I will do the battery test to my cab then call Hartke and go from there. Pretty frustrating that this happened when I thought I followed the manual to a T and I did a bunch of research prior to trying this. Oh well, ya live and ya learn!
     
  18. Unfortunately the only thing you will learn by this is you had a hidden amp head fault ;).
     
  19. Haha true... I blame myself for being so dang adventurous and trying a new configuration
     
  20. Don't blame yourself - you followed the instructions from the manual. Your amp is perfectly safe without a load on either channel. This means that you can run a load on one channel with nothing on the other.

    Bridging an amp allows the full power that the amp is capable of to service one speaker cabinet. Thing is that sheer power is not the way to get appreciably louder. Adding cabinets is. To get twice as loud, you would have to increase power by ten times.

    Edit: Nothing more can be done until the battery test has been performed.

    Edit2: I have been using "stereo" power amps since the late Seventies. I've never felt the need to bridge any of them.
     

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